1. Field of the Invention
The present invention relates to a valve attached to a fuel tank, which is disposed in a fuel tank of vehicles, such as automobiles, and the like.
2. Description of the Related Art
In a fuel tank of an automobile, there is disposed a valve attached to the fuel tank, such as a liquid-fuel flowing-out inhibition valve, an inlet check valve, etc.
Among these valves attached to a fuel tank, the liquid-fuel flowing-out inhibition valve inhibits a liquid fuel from flowing out into a vaporized fuel circulation system. Namely, adjacent to a fuel tank of an automobile, there is disposed a vaporized fuel circulation system, which is referred to as an evaporator circuit. The evaporator circuit introduces a vaporized fuel from a fuel tank into an outside canister, and stores it by adsorbing it on an activated carbon, or the like, thereby inhibiting the increment of the internal pressure, which results from the increment of the vapor pressure, in the fuel tank. The canister is joined to an engine. Accordingly, the vaporized fuel is released from the activated carbon by the inlet negative pressure of the engine, and is mixed into an air-fuel mixture. Thus, the vaporized fluid is again used as a fuel.
In the evaporator circuit, an opening, which is referred to as an evaporator opening, is formed in the fuel tank. The evaporator opening is usually formed at the uppermost portion of the fuel tank in order to inhibit the fuel from flowing in into the evaporator circuit. However, since the liquid surface of the fuel moves up and down, there might be a fear that the liquid fuel flows in into the evaporator opening. When the liquid fuel flows in and arrives at the canister, it adsorbs onto the activated carbon. Accordingly, there might arise a fear that the liquid fuel hinders the usual adsoprtion action of the activated carbon for the vaporized fuel.
Hence, a liquid-fuel flow-out inhibition valve has been disposed conventionally in the fuel tank in order to inhibit a liquid fuel from flowing out from the evaporator opening. For example, in FIG. 16, there is illustrated a cross-sectional view of a conventional liquid-fuel flow-out inhibition valve. The conventional liquid-fuel flowing-out inhibition valve comprises a cover 101 and a case 102. The cover 101 is formed on an upper portion of a fuel tank 100 integrally therewith. The case 102 is provided with an evaporator opening 103, which is formed through an upper portion of the case 102, and a floating valve 105, which is disposed in the case 102, and is engaged with an opening end of the cover 101 by an engagement claw 104. Note that the cover 101 communicates with an evaporator circuit that is not shown. Moreover, an O ring 106 is disposed in a space between an inner peripheral surface of the cover 101 and an outer peripheral surface of the case 102, and secures a liquid-proof ability.
Among the valves attached to a fuel tank, the inlet check valve inhibits a fuel and a vapor, held in a fuel tank, from flowing inversely when supplying a fuel. Namely, the fuel, which is supplied through a fuel supply opening, flows in into the fuel tank. At this moment, there might be a fear that the fuel and the fuel vapor, held in the fuel tank, flows inversely back to the fuel supply opening.
Hence, an inlet check valve has been interposed conventionally between a fuel filler pipe and a fuel tank in order to inhibit the fuel, and the like, from flowing inversely. For example, in FIG. 17, there is illustrated a cross-sectional view of an inlet valve set forth in Japanese Unexamined Patent Publication (KOKAI) No. 2,001-163,069. The inlet check valve 200 comprises a cylinder-shaped case 202, in which a valve body 201 is provided. An O ring 208 is fitted around an upstream-side outer peripheral surface of the case 202. Moreover, a fastening flange 209 is disposed on the outer peripheral surface. Then, an engagement claw 203 is formed at the peripheral edge of the fastening flange 209. While, a cylinder-shaped portion 206 is disposed on an outer wall of a fuel tank 205 protrudingly therefrom and integrally therewith. An engagement step 207 is disposed around an upstream-side outer peripheral surface of the cylinder-shaped portion 206. Then, the inlet check valve 200 is installed to the fuel tank 205 by engaging the engagement claw 203 of the case 202 with the engagement step 207 of the cylinder-shaped portion 206. Moreover, the O ring 208 contacts with an inner peripheral surface of the cylinder-shaped portion 206 elastically, thereby securing a sealing ability.
However, the above-described conventional liquid-fuel flow-out inhibition valve is associated with the following problems. First, since, the case and the cover is connected by the claw engagement, the connected portions merely scatter by the number of the claws on the case. Moreover, even when only one of the plurality of claws disengages, the swinging of the case might occur so that there might be a fear that the other claws disengage one after another successively. Moreover, the connected portions are usually immersed into the fuel. Accordingly, because of the swelling of the component members, there might arise a fear that the engagement claws are all the more likely to disengage. In view of these causes, it might be impossible to say that there might be no fear that the engagement claws disengage to come off the case from the cover.
Second, as described above, the liquid fuel flows out mainly from the evaporator opening. However, since the claw engagement is not good inherently in terms of the liquid-proof ability, there might arise a fear that the liquid fuel flows out through the space between the case and the cover. Accordingly, in the conventional liquid-fuel flow-out inhibition valve, the O ring is disposed in the space between the case and the cover, but is an extravagant component member. Namely, it is necessary to give a liquid-proof ability to the space between the case and the cover to a certain extent or more, but it is necessary to give an excessive liquid-proof ability thereto to such an extent that an O ring is disposed therein. When an O ring is provided in a liquid-fuel flow-out inhibition valve, the number of the component parts increases by the quantity. Moreover, a process for assembling the O ring is required, and consequently the manufacturing cost of the liquid-fuel flow-out inhibition valve goes up.
Here, in order to reduce the number of the component parts and in order to secure a liquid-proof ability to a certain extent or more, it is possible to think of the following arrangements. For instance, the cover and the case are connected by the claw engagement, but, in addition thereto, ribs and roots are disposed on the outer peripheral surface of the case and the inner peripheral surface of the cover, respectively, so that the space can be formed in a zigzagged manner between the case and the cover. However, the arrangements additionally require manufacturing steps for processing the outer peripheral surface of the case and the inner peripheral surface of the cover, and consequently the manufacturing cost increases. In addition, because of the complexity of the configurations, the arrangements cannot be applied to small-sized liquid-fuel flow-out inhibition valve.
While, in the conventional inlet check valve, the case and the fuel tank are bonded by the claw engagement similarly to the above-described conventional liquid-fuel flow-out inhibition valve. As a result, the conventional inlet check valve might have a problem that it is inferior in terms of the bondability. Moreover, the O ring is disposed in the space between the case and the fuel tank. Thus, the conventional inlet check valve suffers from a problem that the number of component parts is large. Namely, the conventional inlet check valve is associated with problems similar to those of the conventional liquid-fuel flow-out inhibition valve.